82 lines
2.8 KiB
Markdown
82 lines
2.8 KiB
Markdown
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# Interpreter
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## Status
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Proposed
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Proposed by: Adam Gibson (28-09-2020)
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Discussed with: N/A
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## Context
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## Decision
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An interpreter uses the [import IR](./0003-Import_IR.md) and the [mapping rule IR](./0004-Mapping_IR.md)
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to execute and map operations from one framework to nd4j's file format and back.
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This also allows execution of different frameworks via conversion in the nd4j engine.
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A combination of the 2 allows a uniform interface to be used for the interpreter.
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1 or more MappingRules will be used to transform 1 file format to another.
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## Mapping Rules Execution
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Mapping Rules are named functions that contain the function signature
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(input and outputs). These mapping rules are used by the interpreter
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to know which functions to execute.
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The interpreter has built in implementations of the defined functions
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for the desired transforms.
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## Import process
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An import process is defined for an overall framework.
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It maps input graphs to samediff graphs using
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specified mapping processes for op names and frameworks.
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An import process is all that is needed to create a graph.
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Below are the needed concepts for an import process to implement.
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## Graph creation
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In order for execution to happen, a graph needs to be built.
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This happens in java via the samediff builder.
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The conversion happens as follows:
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input node -> convert node to op descriptor via defined mapping rules -> add op descriptor to graph
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The op descriptor is converted to a CustomOp which is then added to the graph via
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[addArgsFor](https://github.com/KonduitAI/deeplearning4j/blob/88d3c4867fb87ec760b445c6b9459ecf353cec47/nd4j/nd4j-backends/nd4j-api-parent/nd4j-api/src/main/java/org/nd4j/autodiff/samediff/SameDiff.java#L1078)
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This handles declarative graph creation setting dependencies up. Delegation of the graph structure
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creation to the existing Samediff library enables the scope of this interpreter to be focused on
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mapping operations.
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## Custom Sub graphs
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One common use case is mapping sub graphs to custom layers. A custom layer can be thought of as a sequence of operations.
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In order to map this, a named process can be created. Generally, if you know what ops the sub graph is made of,
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you only need to declare a set of rules based on the rules that map individual ops in the existing framework.
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## Consequences
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### Advantages
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* Uses a common interface across different frameworks making maintenance simple
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* Allows an easy to maintain abstraction for interop with different file formats
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* Allows an easy entry point in to the framework without knowing much about the framework.
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### Disadvantages
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* Need to ensure compatibility across different frameworks
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* Requires extensive testing to ensure proper compatibility
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* May not necessarily support all ops people are expecting. This will be addressed
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in a new ADR.
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